Off-Resonance TROSY (R1ρR1) for Quantitation of Fast Exchange Processes in Large Proteins

Abstract
Current solution NMR experiments for characterizing conformational exchange processes in large proteins are limited to exchange rates ca. 500−3000 s-1. A TROSY-based constant relaxation time (R R1) experiment is designed to extend this capability to measure motion with rates up to 105 s-1 in large macromolecules. The experiment combines off-resonance spin-lock rf fields, which provide access to the faster time-scale dynamics, with TROSY coherence selection, which extends the molecular-weight range available for study. When implemented on the 53-kDa dimeric enzyme triosephosphate isomerase, the experiment yielded substantial gains in signal-to-noise (up to 60%) over current experiments at modest static magnetic fields (14.1 T). The TROSY (RR1) experiment should therefore be of general utility for investigation of fast conformational exchange events in large proteins.

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